Thiodipropionates-polythene antioxidants



Patented Aug. 22, 1950 H MyersTI"Gribbinsfwilmingtpn, men, assignor to :I.. :du .Pont de: emours .'=Gompany, Wilming'tton; ,Dch, ;a-=corparation woflilelawane No Drawing.

W 'Jnencaptoethyl, .mercaptopropyh .mercaptobutyl,

2,188 ,465, Q01! .rbM CDHtRCtil-QE ethylene: with Water and aperoizy compound catalyst, preferably a diacyP'per Xide or a dialkyld'ibxide, at temperatirresi*of"from 40 "to-350 G. and at pressures in atmospheric; pre'ferablyin the range of .50 to 3000 atmospheres. filhespolymers of ethylene,, corresponding in composition substantially in properties from liquids to solids and *scften-o'r melt between about 100 C. and about 120 0., their melting point being substantially independent of their molecular weight.

. It is an object of thi invention to provide compositions comprising ethylene polymers which have improved physical and electrical stability. Another object is to provide compositions comprising ethylene polymers which in the form of self-supporting films, molded articles, fibers, or coatings, are stabilized against degradation. Still another object is to provide new composi tions comprising as a major component; ethylene.

polymers, and as a minor component, an ester" of beta-thiodipropionic'acid; "Otherbbjects will appear hereinafter.

The above objects are accomplisfi'e'd'acmrdiiig'. to this invention by incorp ratingzrintoanormally solid ethylene polymer a smallampunt of a beta-thioether of an-ester -;of--propionic-aeid;--

and li ind of Stabilizationdesired. LIhevamount having the formula a Roooomor'ns-x droxyethyl, and hydroxybutyl; the ether groups:

methoxymethyl, methoxyethyl, and ethoxyethyl; the acid groups and the-R esters thereof: carboxymethyl, carboxyethyl, carboxypropyl and carboxybutyl; and the aldehyde groups such as aldehydoethyl.

3. A sulfur-hydrocarbon group such as e. g.:

Applicationjseptenrber 25.1946, Serial No. ceman sol-aims;- (o1. 260 45.85)

mercaptoisobutyl, .mercaptohexyhand ethiaethyl. 4. A sulfurand oxygenated-hydrocarbon group such as e. g. Carboxyethiaethyl, -CHzGI-I2*SCHzCHzCOOH; Carboxyethiaethdithiaethyl,

, CH2CH2SSCH2CH2SCH2CH2COQH; Carboxyethiaisobutyl,

*Carboxyethiapropyl, V

. CH2CH2CH2SCH2CH2GOO'H, .:and 5. A sulfur-, nitrogen-hydrocarbongroup such as e. g.: 3-benaothiazyl mercaptopropion'ic acid, which compounds are more specificallyadescribed the Gribbins, Miller and OLeary "patent, U. S. 2,397,960. Theseesters'may "be mixed' -with' the polymer in any suitable manner that will efiec't thorough distribution. 'Thiscan be 'accomplish'ed in 'a, machine suitablefor mixingsolids orincorporating liquids, as by milling *the ethylene polymer with th'e -addition agent on heated rolls; such as 'are usedrin'thercompounding of rubber, or on other su it abl.e milling or mixing equipment, such for example, 'asthe'Banbi-Iry'miXer. Instead of addingthe agent tothe polymer in the solid or ino'ften' state, "it can'be added "to a solution or suspension of' polymer in -an-organie-solvent'or-to'an ventsubseguently removed by vaporization.

1 In general, the amount of'agent to be added to "the'ethylenepolymer depends upon-the-degree -ofagent added can vary from 0.001% to 5.0% based on the weight of the ethylene polymer, but as a rule it is preferred to use the minimum amount required to achieve the desired results. The amount commonly used will vary from 0.005 to 2.0 parts by weight per hundred parts ethylene polymer.

In one form of practicing the invention, the ethylene polymer, such, for example, as a solid polymer having a molecular weight of about 4,000, is dissolved in a hot organic hydrocarbon solvent, e. g., xylene, and to this solution i added the ester in amount sufiicient to give the desired amount of the agent, based on the weight of the polymer. These solutions are cast on steel plates; the thickness of the film is adjusted so as to give a dry film of about 1 mil in thickness; the solvent is removed by evaporation, and, after drying, the film is stripped from the plate.

The examples which follow illustrate the utility and the outstanding advantages of this invention:

Example 1.A solid polymer of ethylene obtained by polymerization at a temperature of about 200 C., a pressure of about 1000 atmospheres and in the presence of a peroxide catalyst and having a molecular weight of at least 4,000 was worked on the rolls of a steam heated rubber mill until a continuou sheet was formed. This required about 0.5 minute at roll temperatures of 170 C. Sufllcient dilauryl beta-thiodipropionic; acid was then sprinkled on the mill bank to give 0.2% thereof based on the polymer. The milling, was continued at 170 0., material being removed from the mill at intervals, compression molded into a suitable shape, and the power factor of the compound determined. Duplicate samples of polymer were treated. In one case, no ester was added; in another, 0.2% thiodipropionic acid; and, in another, 0.2% distearyl thiodipropionate. I

TABLE I Efiect of milling at 170 C. of polyethenes' with T DP stabilizers on power factor at 106 me.

0 2% Stabilizer None 'IDP Acid Power FactorXlO i Dilauryl TDP=Mixture of higher alcohol esters (mostly laur alcohol) of 'IDP.

; Example 2.On outdoor exposure tests the superiority of the protected polymers over the un- The di-higher alkyl beta-thiodipropionates and especially the dilauryl and distearyl esters have been found to be outstanding in their ability both tcprotect the polymers of ethylene from degradation on exposure to the elements and to preserve their vvaluable electrical low-loss characteristics at high frequencies during exposure to high temperatures in contact with air.

v 7 I claim:

1. A composition of matter comprising a solid ethylene polymer and from 0.001 to 5.0% by weight of dilauryl beta-thiodipropionate.

2.-- A composition of matter comprising as the major component a normally solid polymer of ethylene and 'from 0.005 to 2.0% by weight of distearyl beta thiodipropionate.

.3. A composition of matter comprising a solid polymer of ethylene and from 0.001 to 5% by weightof-a dialkyl ester of beta-thiodipropionic acid. I

v 1 MYERS F. GRIBBINS.

REFERENCES CITED 'The following. references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,140,545: Pier D80. 20, 1933 Gribbins et a1. Apr. 9, 1946 OT ER REFERENCES l folythene, b Hahn et a1., Ind. & migfcnem. vol. 37, June 1945, pages 530-531.

protected polymers is evident from the data of Table II,-the agent haying been incorporated in the polymer of this table substantially in accord with the process as described in Example 1.

TABLE II Results of Wilmington outdoor exposure test cf polythene with dz lauryl TDP Iniiibit rQ"; None, Control 1% Dilauryl TDP 21 Wks. 34 Wks. 21 Wks 84 Wks. Exposure. None Nov; ov.- None N ov.

' April July P July Cold Brittleness, Temp., C OK-72 0K-72 7 OK-72 011-72 OK-72 

3. A COMPOSITION OF MATTER COMPRISING A SOLID POLYMER OF ETHYLENE AND FROM 0.001 TO 5% BY WEIGHT OF A DIALKYL ESTER OF BETA-THIODIPROPIONIC ACID. 